Overview
Congenital myopathy with fiber size variation is a rare inherited muscle disorder that is present from birth or early infancy. The term 'OBSOLETE' in its name means that this condition has been reclassified in medical databases and may now fall under a broader category of congenital myopathies. Congenital myopathies are a group of muscle diseases caused by problems in the structure or function of muscle fibers. In this particular condition, a muscle biopsy shows that the muscle fibers vary significantly in size, which is not normal. This variation in fiber size leads to muscle weakness, typically affecting the limbs, face, and sometimes the muscles used for breathing. Patients with this condition usually show signs of muscle weakness early in life, such as low muscle tone (floppiness) at birth, difficulty feeding, delayed motor milestones like sitting or walking, and general muscle weakness. The severity can range from mild to severe. Some children may have difficulty breathing on their own and may need respiratory support. There is currently no cure for congenital myopathies, including this subtype. Treatment focuses on managing symptoms and improving quality of life. This includes physical therapy to maintain muscle strength and flexibility, respiratory support if breathing muscles are affected, and nutritional support if feeding is difficult. Because this diagnosis has been reclassified, patients previously diagnosed with this condition should work with their medical team to determine if a more specific genetic diagnosis is now available, which could guide more targeted management.
Key symptoms:
Muscle weakness from birthLow muscle tone (floppiness)Delayed motor milestones like sitting and walkingDifficulty feeding as a babyBreathing difficultiesFacial muscle weaknessThin or underdeveloped musclesJoint contractures (stiff joints)Scoliosis (curved spine)Fatigue and low enduranceDifficulty swallowingHigh-arched palate
Variable
Can be inherited in different ways depending on the underlying gene
Neonatal
Begins at or shortly after birth (first 4 weeks)
Treatments
No FDA-approved treatments are currently listed for OBSOLETE: Congenital myopathy with fiber size variation.
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Specialists
View all specialists →No specialists are currently listed for OBSOLETE: Congenital myopathy with fiber size variation.
Treatment Centers
8 centersBaylor College of Medicine Rare Disease Center ↗
Baylor College of Medicine
📍 Houston, TX
🏥 NORDStanford Medicine Rare Disease Center ↗
Stanford Medicine
📍 Stanford, CA
🔬 UDNNIH Clinical Center Undiagnosed Diseases Program ↗
National Institutes of Health
📍 Bethesda, MD
🔬 UDNUCLA UDN Clinical Site ↗
UCLA Health
📍 Los Angeles, CA
🔬 UDNBaylor College of Medicine UDN Clinical Site ↗
Baylor College of Medicine
📍 Houston, TX
🔬 UDNHarvard/MGH UDN Clinical Site ↗
Massachusetts General Hospital
📍 Boston, MA
🏥 NORDMayo Clinic Center for Individualized Medicine ↗
Mayo Clinic
📍 Rochester, MN
👤 Mayo Clinic Center for Individualized Medicine
🏥 NORDUCLA Rare Disease Day Program ↗
UCLA Health
📍 Los Angeles, CA
Travel Grants
No travel grants are currently matched to OBSOLETE: Congenital myopathy with fiber size variation.
Community
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Caregiver Resources
NORD Caregiver Resources
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Mental Health Support
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Family & Caregiver Grants
Financial assistance programs specifically for caregivers of rare disease patients.
Social Security Disability
Learn how rare disease patients may qualify for SSDI/SSI benefits.
Questions for your doctor
Bring these to your next appointment
- Q1.Has genetic testing been done to identify the specific gene causing this condition?,Since this diagnosis is now considered obsolete, is there a more specific diagnosis that applies to my child?,How often should my child's breathing and lung function be monitored?,What physical therapy program is recommended, and how often should sessions occur?,Are there any clinical trials or new treatments being studied for this type of myopathy?,What emergency signs should I watch for, and what should I do if they occur?,Should other family members be tested for this condition?
Common questions about OBSOLETE: Congenital myopathy with fiber size variation
What is OBSOLETE: Congenital myopathy with fiber size variation?
Congenital myopathy with fiber size variation is a rare inherited muscle disorder that is present from birth or early infancy. The term 'OBSOLETE' in its name means that this condition has been reclassified in medical databases and may now fall under a broader category of congenital myopathies. Congenital myopathies are a group of muscle diseases caused by problems in the structure or function of muscle fibers. In this particular condition, a muscle biopsy shows that the muscle fibers vary significantly in size, which is not normal. This variation in fiber size leads to muscle weakness, typica
At what age does OBSOLETE: Congenital myopathy with fiber size variation typically begin?
Typical onset of OBSOLETE: Congenital myopathy with fiber size variation is neonatal. Age of onset can vary across affected individuals.